Now I can reply to my own post. After blundering around various sites I found the answer at http://www.scyld.com/expert/irq-conflict.html Essentially, the BIOS Setup option "Plug and Play OS" must be OFF. Hope this post in the archive helps some other newcomer! Jack Dodds wrote:
I cannot get the 3c905-tx to work at all. This is probably because it is being configured to use IRQ 0. During boot from CD, or after installling a minimal system, I get the message (approximately) eth0: 3com 3c905c Toronado at 0xb400 IRQ 0 Warning: IRQ 0 is not likely to work